Ash/Tephra Fall

Numerous hazards can occur at composite volcanoes like Mount Jefferson including lava flows and domes, pyroclastic flows, ballistics, tephra fall, lahars and debris avalanches.

Mount Jefferson is a prominent feature of the landscape seen from highways east and west of the Cascades. The volcano has erupted repeatedly for hundreds of thousands of years beginning about 300,000 years ago.

Eruptions from Mount Jefferson, a nearby monogenetic vent, or a more distant volcano has the potential to impact the local communities, especially those downwind of the tephra plume.